add "skip.sass=1" to local.properties in your app or workspace folder. That file will not exist in either location but is designed to contain local (as in per-individual) build overrides that apply to the app or all apps in the workspace. This will allow the overall build to run but obviously skips compass.

tweak the body of the "-sass" target in .sencha/app/build-impl.xml to either use the full path to compass or something more general (like a new property) depending on if you are trying to share the project with others.